Acid treatment of oils



i'i'ED ST'i' 'f d TET OFFIC 2,337,826 AGED TREATMENT OF OILS Milton W. Lee, Palos Verdes Estates, Calif., as-

signor to Union Oil Company of California, Los Angcles, Califl, a corporation of California No Drawing. Application December 2, 1940, Serial No. 368,224

8 Claims. (Cl. 196-31) This invention relates to a process for desulhigh molecular weight petroleum fraction, such furizing oils and is particularly directed to deas residuum obtained from topping an asphalt sulfurizing such high sulfur content gasoline conbase crude oil, a greater reduction in sulfur constituents as pressure distillate made by cracking tent is obtained than when the acid treatment residuum or gas oil containing a high percentage is carried out in the conventional manner in the of sulfur. absence of such additive. For example, I have It is well known to treat high sulfur content obtained a 29% greater reduction in sulfur conoils, such as cracked gasoline, with sulfuric acid tent by the use of my process over the convenin order to reduce the sulfur content of the oil. tional process using no heavier petroleum frac- This method has heretofore required the use of 10 tion. To illustrate, a pressure distillate obtained relatively large quantities of sulfuric acid usually from the viscosity reduction of a Los Angeles Bacf at least 98% strength. sin crude oil residuum, which pressure distillate It is a principal object of my invention to procontained 1.35% by weight of sulfur (in the form vide a process which will more efiiciently utilize of various organic sulfur compounds) was mixed th quantity of acid employed for removing 5111- at a temperature of about 80 F. with about 1% of fur compounds from high sulfur gasolines such an asphalt obtained by the vacuum distillation as pressure distillate. of a Santa Fe Springs crude oil, the asphalt hav- A further object of my invention is to obtain ing a m l in p n of 5 F. n a p e ra n ahigher yield of stable cracked gasoline containof 6 at 77 F. The mixture was then shaken ing less sulfur and having less odor than a 20 vigorously at room temperature with acid in the cracked gasoline treated with the same amount at o of 10 lbs, f Sulfuric acid D barrel of of acid by previously known procedures, pressure distillate. The mixture was allowed to Other objects, features and advantages of my settle in order to separate the acid and reaction invention will become apparent from the followproducts f om t e treated O l. The Oil was deing detailed description. canted from the settled sludge and was then As is well known, one of the conventional washed twice with water using 50% by volume of processes for reducing the sulfur content of Water in the fi Wash and y volume in cracked gasolines consists in mixing or contacting the second Wash. The oil was then washed with the pressure distillate with sulfuric acid, prefer- 1 of an aqueous lu i n ntainin 2% by ably of 98% strength or stronger, which reacts Weight of caustic soda. This w wed y with impurities contained in the gasoline includanother W it y o e o ate The ing the sulfur and sulfur compounds. The mixf re in W h we e mp h y shaking ture is allowed to settle and the sulfuric acid the distillate n e aqueous s lu i n eth r phase containing dissolved impurities is separated at room p a e and e a wi t e i n the form of a sludge from the treated'pressure ture to stratify into two layers and drawin th distillate. The latter is then washed one or more aq ayer from the oil. times with water and is then treated with a. weak The thus treated oil was then redistilled with alkali solution such as caustic soda. The alkali steam at a maximum temperature of 450 F. to treated pressure distillate may again be washed remove approximately 95% of the treated preswater after which it is redistilled to produce 40 sure distillate as an overhead fraction. The thus a gasoline distillate of the desired boiling range. treated pressure distillate when tested showed a The treated and redistilled pressure distillate may sulfur content of 0.73% by weight. be caustic washed to remove traces of acidic me- In order to compare the fore oin p o ess with teriais formed during the distillation, and may the conventional methods in which no additive then be further treated with sulfur in the presis employ he foregoing mp w r p t ence of doctor solution which consists of sodium Without the use of the additive but under condiplumbite. This final treatment sweetens the gastl'ons of separation and quantities of material oline by converting mercaptans into less odorous ployed similar to those of the foregoing examp sulfur compounds. A test on the thus treated pressure distillate The present invention is directed to an imshowed a sulfur content of 0.87% by weight. provement in acid treating sulfur containing gas- In the conventional process, the redistillation oline stocks. I have discovered that when the of the acid treated pressure distillate is someacid treatment of the sulfur-bearing pressure distimes accomplished in the presence of a small tillate is carried out in the presence of a small amount of additive similar to that employed by amount of an additive consisting of a relatively app nt during acid treatment. Such additive is known as artificial bottoms and is added purely for the purpose of assisting in the distillation as many stills require a certain volume of bottoms material to be produced in order to operate properly. In order to show that the acid treatment in the presence of the additive produces a different result from that obtained by the redistillation in the presence of the additive but without employing the additive during the acid treatment step, the foregoing process was repeated except that no additive was added during the acid treatment but was added to the acid treated pressure distillate immediately prior to the redistillation. A test on the distillate thus produced showed a sulfur content of 0.88% which is not substantially different from the 0.87% obtained in the above process when no additive was employed either during the acid treatment step or during the redistillation step. This comparison illustrates that the beneficial effect of the process forming the subject matter of my invention is due primarily to the acid treatment in the presence of the additive and is not the same as redistillation of the acid treated distillate in the presence of the additive.

In some instances the finished oils treated by the proposed process had a better odor than products from the corresponding conventional treatments. Furthermore, it was possible to take more material of acceptable quality overhead during the redistillation when using the proposed method of acid'treatment ratherthan the conventional one.

While I prefer to employ as an additive for the acid treatment step a material containing asphalt such as a residuum obtained from topping an asphalt base crude oil, a road oil, or an asphaltcontaining crude oil, I have found other petroleum fractions having a molecular weight substantially higher than that of the gasoline to be treated, to be operative in obtaining a greater sulfur reduction in'the acid treatment than is obtainable without their use under similar treating conditions. Examples of such additive are lubricating oil fractions including the extracts or rafiinates obtained upon extracting the lubricating oil with liquid sulfur dioxide or other selective solvents, paraffin wax, petroleum resins or plastics, oxidized petroleum fractions such as oxidized lubricating oils, paraflin wax, asphalt,

etc. In addition, other high molecular weight materials of hydrocarbon character, such as coal tar, coal tar pitch, etc., may be employed as additives.

The amount of additive which is to be employed may vary with the particular additive with which the stock is to be acid treated and the strength and amount of acid employed. In general, I have found that about 0.5 to 5% by weight of the additive is sufficient for the purpose.

The strength of the acid will also vary with the stock and conditions of operation. Generally, sulfuric acid of 98% strength or greater is suitable forthe purpose. The amount of acid to be employed will vary with the amount of sulfur desired to be removed, it being understood that a greater amount of the acid will remove a greater amount of sulfur. The temperature of the acid treatment will vary from the very low sub zero temperatures to the more elevated temperature of approximately 100 F. or more.

While the foregoing description of my invention has been directed to the treatment of gasoline constituents of high sulfur content, such as pressure distillate, it will be understood that the invention is applicable to the acid treatment of other petroleum or hydrocarbon fractions for sulfur removal, such as kerosene, gas oil, lubricating oil, benzene, xylene, etc., the only requirement being that the additive have a substantially higher molecular weight than the stock to be acid treated.

As is conventional in the desulfurization of oils, the acid treatment may be followed with water washing and neutralization with an aqueous solution of caustic alkali which may also be followed by a water wash and the thus treated pressure distillate may be redistilled to remove or more as an overhead fraction to leave a portion of the material as bottoms which will containsulfur compounds. Since the acid treatment is effected in the presence of a high molecular weight material, substantially all of this material will be contained in the bottoms, resulting from the redistillation. If desired, these bottoms may be recirculated; or a further quantity of the additive may be incorporated into the pressure distillate prior to the redistillation. The acid treated pressure distillate may be further treated, for example, sweetened by the doctor treatment or any other sweetening process.

The above description of my invention is not to be considered as limiting but only as illustrative of the invention as many variations may be made within the scope of the following claims.

Iclaim:

1. A process for treating a gasoline distillate containing sulfur-bearing compounds which comprises adding to said distillate a hydrocarbon fraction having a higher boiling point than said distillate and then treating said mixture at a temperature between about 0 F. and F. with concentrated sulfuric acid.

2. A process for treating a gasoline distillate containing sulfur-bearing compounds which comprises adding a hydrocarbon fraction containing asphalt to distillate and then treating said mix ture at a temperature between about 0 F. and 100 F. with concentrated sulfuric acid.

3. A process for treating a gasoline distillate containing sulfur-bearing compounds which comprises adding asphalt to said distillate and then treating said mixture at a temperature between about 0 F. and 100 F. with concentrated sulfuric acid.

4. A process for treating a gasoline distillate containing sulfur-bearing compounds which comprises adding to said distillate approximately 0.5 to 5% by weight of a distillation residue of an asphalt-containing crude oil and treating said distillate at a temperature between about 0 F. and 100 F. with concentrated sulfuric acid in the presence of said residue.

5. A process for treating a gasoline distillate containing sulfur-bearing compounds which comprises mixing said distillate with a relatively small amount of a relatively high boiling point petroleum fraction and treating said mixture at a temperature between about 0 F. and 100 F. with concentrated sulfuric acid of such concentration and quantity to reduce the sulfur content of said distillate to the desired amount.

6. An improvement in the process of acid treatin-g cracked distillates for reduction of gum and sulfur content, which comprises mixing said cracked distillate with approximately 0.5 to 5% by weight of a distillation residue of an asphaltcontaining crude oil, before contacting the said mixture at a temperature between about 0 F. and 100 F. with concentrated sulfuric acid, sepsulfur content, which comprises mixing said cracked distillate with approximately 0.5 to 5% by weight of a distillation residue of an asphaltcontaining crude oil, before contacting the said mixture at a temperature between about 0 F. and 100 F. with strong sulfuric acid, separating the resulting sludge from the treated oil, and distilling said oil to the desired end-point.

MILTON W. LEE. 

